Micro Groove Machining Characteristics of Si3N4-hBN Composites

초록

Si3N4 composites are known as very difficult-to-cut materials because of its high strength and hardness. Their machining mechanism is much different with metals, which can be characterized by cracking and brittle fracture due to relatively high strength and temperature resistance. However, Si3N4-hBN composite materials are well known as one of the machinable ceramics, which can be easily machined with hard-alloy cutting tools under proper machining conditions. Also, the needs for micro parts using such materials are rapidly increasing in related application fields. In this study, the analysis of micro groove machining characteristics of Si3N4-hBN composites are performed to determine optimum micro machining conditions for those applications. As a first step, the R-curve behavior of the Si3N4-hBN composites is investigated to understand its machinability. It can be observed that the R-curve rose slowly for this material so that the fracture toughness is low at small cracks but high at long cracks. Then, a set of micro groove machining experiments are performed to investigate the micro groove machining characteristics with variable h-BN contents and different conditions. Also, cutting forces and tool life are measured for each experimental condition. From the results, it can be investigated that the cutting forces decrease and tool life increases with the increase of h-BN contents. It can be concluded that the results of this study can be applied for the micro parts production using Si3N4-hBN composites.